* Key in the ignition: Sounds obvious, but double-check that the key is fully removed from the ignition switch. Sometimes a part of the key might remain slightly engaged.
* Driver's side door ajar: The chime often warns about an open driver's side door. Make sure the door is completely closed and latched. Check the door latch mechanism itself; it might be faulty and not properly engaging.
* Passenger's side door ajar (or other doors): While the driver's side is most common, the chime might also sound for other open doors. Check all doors and the tailgate/rear hatch.
* Hood ajar: A slightly open hood can also trigger the chime.
* Faulty door ajar switch: One or more of the door ajar switches (located within the door jambs) might be malfunctioning. They can become corroded, worn out, or misaligned, sending a false signal to the vehicle's computer. This is a very common cause.
* Faulty ignition switch: Although less likely than a door switch issue, a problem with the ignition switch itself could also be causing the persistent chime.
* Body control module (BCM) issue: The BCM controls many electrical functions, including the chime. A fault within the BCM could cause it to malfunction and sound the chime inappropriately. This is less likely but possible.
Troubleshooting Steps:
1. Check all doors, hood, and tailgate/rear hatch: Ensure they're completely closed and properly latched. This is the first and easiest step.
2. Inspect the door ajar switches: Locate the switches in the door jambs (usually near the striker plate). Visually inspect them for damage or corrosion. You can try gently cleaning them with electrical contact cleaner.
3. Try starting the vehicle with only the driver's side door closed: If the chime stops, you know the problem is with another door switch.
4. Test the switches (advanced): You can use a multimeter to test the continuity of the door ajar switches to confirm their functionality. (This requires some electrical knowledge.)
5. Consult a repair manual: A repair manual specific to your 1997 Ford Aerostar will provide detailed information on testing the switches and other components related to the chime system.
6. Seek professional help: If you're not comfortable troubleshooting electrical systems, take your Aerostar to a qualified mechanic. They can diagnose the problem accurately and repair it efficiently.
Start with the simplest checks (doors, hood) before moving on to more involved troubleshooting. The faulty door ajar switch is a strong contender given the symptoms.
